textproduct: Quad Cities

KEY MESSAGES

- An active pattern is in store next week with multiple rounds of showers and storms likely through Friday. Currently, the greatest severe potential is Monday PM when there is a Marginal Risk, Level 1 out of 5, for eastern IA and northwest IL.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 230 PM CDT Sat Sep 12 2026

As of early this afternoon, a weak cold front was positioned near the Mississippi River. Humidity is much lower to the northwest of the front with dewpoints in the 50s, compared to mid/upper 60s to the east into northwest/central Illinois. Weak convergence along the boundary and the absence of forcing aloft should preclude showers/storms through this afternoon and evening across eastern Iowa and northwest Illinois. Heading into tonight, subtle WAA aloft along an axis of 850-700mb westerly flow could kick off scattered showers and isolated storms mainly after 3 AM, likely becoming more widespread later into Sunday morning (20-50%).

As an upper wave works across the region during the day on Sunday, scattered showers and isolated thunderstorms will continue to be possible through the afternoon, with relatively light rainfall amounts anticipated. Northerly surface winds, combined with periods of cloud cover, will act to hold down temperatures into the low/mid 70s for most locations for Sunday PM. With a drier air mass in place for Sunday night, cool conditions are expected with lows in the upper 40s NE to upper 50s SW.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 230 PM CDT Sat Sep 12 2026

Monday-Tuesday...The longwave ridge over the Northern Rockies shifts eastward over the Mid-to-Upper Mississippi Valley as a closed heights center replaces it over the Northern Rockies. Diffluent flow aloft and strong low-level WAA should support storms (50-80% coverage) along the warm front in eastern Iowa, but limited moisture, especially near the surface, will put a hamper on the coverage (20-40%) across west-central and northwest Illinois. Regardless, the southerly return flow behind the warm front is forecasted to allow dew points to climb back into the upper 60s and low 70s along the cold front diving southeastward as the trough over the Northern Rockies lifts into south-central Canada. After another dry period Monday afternoon, storms will once again redevelop Monday evening along the approaching cold front where a 40-knot LLJ is expected to enhance the low-level shear. Current LREF guidance has the sfc-to-500 mb wind shear vector oriented at a 45-degree angle and close to 35 knots which would suggest a mixed convective mode. However, by the time any convection reaches our CWA, it will likely be in the form of linear clusters, promoting a more damaging wind threat. This is why the SPC has a Marginal Risk, Level 1 out of 5, for severe storms Monday night in our northwestern counties.

By Tuesday, the storms are expected to decrease in intensity along the front as upper-level dynamical support is lost. A weak high pressure is forecasted to slide into Minnesota Tuesday night, reinforcing the northeasterly flow over the CWA and pinning the stationary front in our south. This stationary front will act as the focal point for showers and storms through the middle of next week.

Wednesday-Friday...The entire area will be sandwiched between a ridge over the Southeast and a positively tilted trough over Hudson Bay that extends back towards the Pacific Northwest. This pattern should support diffluent flow aloft over the residual stationary front as rounds of stratiform rain and storms develop along it on Wednesday and Thursday. As the Southeast ridge retrogrades westward, the flow is forecasted to return to a more stable zonal flow as the boundary begins to wash out Friday without any major air mass changes. By the end of the next week though, there is a good chance (50-80%) that areas across eastern Iowa and northwest Illinois will see over 2 inches of rainfall with swaths of 4+ inches possible (20-30%).

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1221 AM CDT Sun Sep 13 2026

VFR conditions are expected over the next 9 hours with mostly clear skies before scattered rain showers approach from the west late morning. With dry air near the surface, ceilings should generally be above 5 kft with the only potential impact to flight category being brief periods of MVFR visibility in moderate SHRA. By 21 UTC, most of the showers should exit the area as skies clear out north of I-80. Winds are forecasted to remain northerly and under 10 knots for a majority of the TAF period at all sites with a possible northeasterly shift for CID, MLI, and BRL after sunset.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.